Planar polymer transistor

ABSTRACT

A structure and method of forming a fully planarized polymer thin-film transistor by using a first planar carrier to process a first portion of the device including gate, source, drain and body elements. Preferably, the thin-film transistor is made with all organic materials. The gate dielectric can be a high-k polymer to boost the device performance. Then, the partially-finished device structures are flipped upside-down and transferred to a second planar carrier. A layer of wax or photo-sensitive organic material is then applied, and can be used as the temporary glue. The device, including its body area, is then defined by an etching process. Contacts to the devices are formed by conductive material deposition and chemical-mechanical polish.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 10/052,151filed Jan. 15, 2002 now U.S. Pat. No. 6,620,657.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to semiconductor technology anddevice designs, and more particularly to an organic-based thin-filmtransistor device and a method for producing the same.

2. Description of the Related Art

Thin-film transistors (TFTs) with active organic layers andpolymer-based electronic components are emerging as an inexpensivealternative to silicon-based TFTs for some applications. The use oforganic and polymeric materials provides two main advantages: First,organic-based devices can be produced using a simpler and less expensivefabrication process in contrast to the expensive equipment andprocessing associated with silicon processing. Second, it is possible tofabricate the devices on flexible plastic substrates due to the abilityto process organic materials at lower temperatures, and due to thegreater mechanical flexibility of organic-based components relative toinorganic materials such as silicon and conductive metals. However,despite considerable research and development effort, organic-based TFTshave not yet reached commercialization, at least, in part, due torelatively poor device characteristics of prior art organic TFTs.

Fabrication of an all-organic TFT requires various organic ororganic/inorganic hybrid materials: semiconductors, insulators, andconductors. The conductor may be selected from conducting polymers suchas polyaniline and poly(ethylene dioxide thiophene), and metal orgraphite colloid particle-based inks. There are a variety of polymericorganic insulators that may be used, such as polyimide or PMMA for thesemiconductor. Organic p-type (hole transporting) and n-type (electrontransporting) materials are both known in the art and have been testedas the semiconductive channel in TFTs. Two relatively simple devicestructures which have been used are the top contact and bottom contact,as shown in FIGS. 1 and 2, respectively. Generally, these devicescomprise a source 1 and drain 2. In the top contact (FIG. 1), the source1 and drain 2 are on top of an organic semiconductor 3, whereas in thebottom contact (FIG. 2), the source 1 and drain 2 are embedded in theorganic semiconductor 3. Below the organic semiconductor 3 is aninsulator 4 in both the top and bottom contact devices. Embedded withinthe insulator 4 is a gate 5. The entire device (both the top and bottomcontact devices) is disposed on a substrate 6.

FET mobilities are generally assessed in the top-contact geometrybecause applying the electrode materials on top of the semiconductorlayer ensures intimate contact. It is desirable to use thebottom-contact configuration for some applications, but in thisgeometry, the contact between the electrode and semiconductor may belimited to a fraction of the vertical wall area of the electrode. Thisresults in increased contact resistance. Problems with bottom-contactdevices are well-known to those skilled in the art. A method to improvethe bottom-contact geometry is to planarize the source and drainelectrodes, which increases the area of contact to the organicsemiconductor. A planar substrate allows for improved semiconductorfilms deposited by spin-coating or printing. However, topography of thebottom source and drain contacts in the prior art causes problems withprinting the organic semiconductor, which would be remedied by using aplanar substrate.

As mentioned, organic p-type (hole transporting) and n-type (electrontransporting) materials are known in the art and have been tested as thesemiconducting channel in TFTs. P-type materials include conjugatedpolymers and linear, conjugated molecules. Examples of p-type conjugatedpolymers include derivatives of regioregular polythiophene described inBao and Lovinger, “Soluble Regioregular Polythiophene Derivatives asSemiconducting Materials for Field-Effect Transistors,” Chem. Mater.,Vol. 11, pp. 2607-2612 (1999), the complete disclosure of which isherein incorporated by reference.

Examples of p-type conjugated molecules include pentacene, which hasbeen extensively studied in TFTs, and further disclosed in U.S. Pat.Nos. 5,946,551; 5,981,970; and 6,207,472 B1; benzodithiophene dimers(Laquindanum et al., “Benzodithiophene Rings As Semiconductor BuildingBlocks,” Adv. Mater., Vol. 9, pp. 36 (1997); phthalocyanines (Bao etal., “Organic Field-Effect Transistors with High Mobility Based OnCopper Phthalocyanine,” Appl. Phys. Lett., Vol. 69, pp. 3066-3068(1996)); anthradithophenes (U.S. Pat. No. 5,936,259); and substitutedand unsubstituted oligothiophenes, originally proposed in Gamier et al.,in “Structural Basis For High Carrier Mobility In Conjugated Oligomers,”Synth. Met., Vol.45, pp. 163 (1991); the complete disclosures of whichare herein incorporated by reference.

There are comparatively fewer n-type organic semiconductors. Examplesinclude 3,4,9,10-perylene tetracarboxylic dilmides described in Struijket al., “Liquid Crystalline Perylene Dilmides: Architecture and ChargeCarrier Mobilities,” J. Am. Chem. Soc., Vol. 122, pp. 11057-11066(2000); 1,4,5,8-naphthalene tetracarboxylic dianhydride (Laquindanum etal., “n-Channel Organic Transistor Materials Based on NaphthaleneFrameworks,” J. Am. Chem. Soc., Vol. 118, pp. 11331-11332(1996));1,4,5,8-naphthalenetetracarboxylic dumide derivatives (Katz et al.,“Naphthalenetetracarboxylic Dilmide-Based n-Channel TransistorSemiconductors: Structural Variation and Thiol-Enhanced Gold Contacts,”J. Am. Chem. Soc., Vol. 122, pp. 7787-7792 (2000)); andmetallophthalocyanines substituted with various electron-withdrawinggroups (Bao et al., “New Air-Stable n-Channel Organic Thin-filmTransistors,” J. Am. Chem. Soc., Vol. 120, pp.27-208 (1998); thecomplete disclosures of which are herein incorporated by reference.

In general, circuitry using organic transistors has the potential ofreduced power consumption and simplicity in the design. However,complementary circuitry using both organic N and P channel transistorsare not common, for example, U.S. Pat. No. 5,625,199, the completedisclosure of which is herein incorporated by reference, teaches atechnique to fabricate complementary circuits with inorganic n-channeland organic p-channel thin-film transistors. Additionally, U.S. Pat. No.5,936,259, the complete disclosure of which is herein incorporated byreference, describes a switch based on a thin-film transistor design(TFT) using a fused ring organic compound as a semiconductor.Furthermore, U.S. Pat. No. 5,804,836, the complete disclosure of whichis herein incorporated by reference, describes an image processor designwhich operates on an array of polymer grid triodes. Similarly, prior artdisclosures also teach a 5-stage ring oscillator using copperhexadecafluorophthalocyanide as the n-channel material andoligothiophenel oligothiophene derivative as the p-channel material.

Two popular structures of an existing polymer thin-film transistor areshown in FIGS. 3(a) and 3(b). These structures have two majordisadvantages. First, the corner thinning problem due to topography, andsecond, the most sensitive portion of the body element is exposed toprocess-induced contamination. The resulting devices have poorperformance and inconsistent properties. Shown in FIG. 3(a) is the firsttypical structure of the polymer transistor. The source 11 and drain 12are first patterned. Then, the body material 13 is deposited andpatterned. The body 13 is a semiconductive polymer or oligomer, and itis applied to the surface of the source 11 and drain 12 islands byevaporation, spin-coating, dip-coating or printing, depending on theorganic semiconductor used. The body material 13 is patterned in one ofthree ways: the most common method is by evaporation of thesemiconductive material through a shadow mask.

The other two methods are printing (i.e., screen printing or inkjetprinting) and using conventional lithography by first applying aprotective coating over the semiconductor, then applying thephotoresist, patterning, and etching. A brief thermal anneal may beneeded, depending on which type of organic semiconductor material isused. The last step includes applying a protective coating to thesemiconductor to passivate the devices from contamination. Afterpatterning the body portion 13, the substrate is wet cleaned. The bodysurface, especially in the channel region, deteriorates due to theunwanted chemical reaction. After a thermal treatment, the body element13 becomes thin around the corners 16, 17 of the source 11 and drain 12due to reflow. Typically, semiconductors decompose before melting. Thesource/drain 11, 12 to body contact area are significantly reduced as aresult of the corner thinning 16, 17 of the body element 13. Then, thegate material 14 is deposited after a thin insulating polymer 15 iscoated on top of the body element 13 and the exposed source 11 and drain12 regions.

Another common structure of the polymer TFT structure is shown in FIG.3(b). The gate 314 is formed first, then an insulating polymer 315 iscoated thereon. Again, the corner thinning presented at the corners 316,317 of the gate 314 causes the possibility of shorting of the source 311and drain 312 to the gate 314. After the source 311 and drain 312 areformed, the body element 313 is formed. In this case, since the body tochannel interface is not exposed to the chemical, the resultingtransistor yield and performance are better than those of the firsttransistor.

In both of the bottom-contact devices described above, there is awell-documented problem with ensuring good contact between theelectrodes and the organic semiconductor. One approach to solving thisproblem has been to modify the surface properties of gold electrodesusing thin, self-assembled monolayers, which improves wetting of theelectrode by the organic semiconductor and which may also decrease thechance of delaminating. However, the topography of the bottom electrodesmay still hamper film formation and reduce the contact area. Therefore,there is a need for a new and improved structure and method forproducing a planar polymer transistor which does not have the problemsinherent with the prior art devices.

SUMMARY OF THE INVENTION

In view of the foregoing and other problems, disadvantages, anddrawbacks of conventional thin-film transistor devices, the presentinvention has been devised, and it is an object of the presentinvention, to provide a structure and method for producing a planarpolymer transistor which does not have the problems inherent with theprior art devices.

In order to attain the objects suggested above, there is provided,according to one aspect of the invention, a process of forming afully-planarized polymer, thin-film transistor by using a first planarcarrier to process a first portion of the device including a gate,source, drain and body elements. Preferably, the thin-film transistor ismade with all organic materials. The gate dielectric can be a high-kpolymer to boost the device performance. Then, the partially-finisheddevice structures are flipped upside-down and transferred to a secondplanar carrier. A layer of wax or photo-sensitive organic material isthen applied, and can be used as the temporary glue. The device,including its body area, is then defined by an etching process. Contactsto the devices are formed by conductive material deposition andchemical-mechanical polish. Unlike the conventional polymer thin-filmtransistor, the invention produces fully planarized devices so thatthere is no corner thinning problem. Another advantage of the newpolymer device is that the most sensitive area of the device, the body,which is made of an organic semiconductor, is fully protected before anyof the processing steps to avoid the possibility of being contaminatedby the environment.

Specifically, a thin-film transistor device and a method of forming thesame is disclosed which comprises forming a first substrate, depositinga first insulating layer on the first substrate, patterning a conductivelayer on the first insulating layer, forming a composite over theconductive layer, depositing a semiconductive layer on the composite,protecting the semiconductive layer with a second insulating layer,applying a thermal treatment to the device, depositing a secondsubstrate on the second insulating layer, inverting the device, removingthe first substrate, bonding the second substrate to a first carrierlayer, etching the composite, depositing a third insulating layer on thefirst insulating layer, and forming contacts through the firstinsulating layer and the third insulating layer.

The method further comprises forming the first substrate in a processcomprising depositing a second adhesive layer on a first carrier layerand depositing the first insulating layer on the first adhesive layer.Moreover, the step of forming a composite comprises depositing a fourthinsulating layer on the conductive layer, wherein the fourth insulatinglayer comprises a higher dielectric constant material than the first andsecond insulating layers.

The method further comprises coating the second substrate with a secondadhesive layer prior to the step of bonding the second substrate to thesecond carrier layer. Moreover, the semiconductive layer comprises afully planarized layer. Additionally, the first insulating layercomprises one of a polyester and a polyimide material. Also, the firstinsulating layer may comprise a polycarbonate material. Furthermore, thefirst and second adhesive layers are one of a photoresist and aphotosensitive polyimide.

The novel features of the present invention are several. Broadly, thepresent invention provides for a high-performance transistor due tounique structural and process flow. Specifically, all functionalcomponents are preferably made of polymeric materials (semiconductive,conductive, low-k insulative, and high-k insulative materials).Furthermore, the carrier is preferably a wafer, glass carrier, orpolymer, and can be rigid or flexible. However, the size is not limitedby the wafer size and is adaptable to large format carriers. Also, theentire structure, including the semiconductor body, gate, source/drain,the interface between the body and the gate, and the drain/source areall fully planarized so that there is no electrical performancedegradation due to the corner thinning between the semiconductor bodyand the source/drain region. Moreover, the structure is fabricated in asimple and cost-effective manner which allows for the fabrication ofboth N-FET and P-FET transistors. Finally, the semiconductor body isplanarized and its interface with the source/drain and gate dielectricis fully protected from subsequent processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects and advantages will be betterunderstood from the following detailed description of a preferredembodiment(s) of the invention with reference to the drawings, in which:

FIG. 1 is a side view schematic diagram of a conventional transistordevice;

FIG. 2 is a side view schematic diagram of a conventional transistordevice;

FIG. 3(a) is a side view schematic diagram of a conventional transistordevice;

FIG. 3(b) is a side view schematic diagram of a conventional transistordevice;

FIG. 4 is a side view schematic diagram of a partially completedthin-film transistor device according to the present invention;

FIG. 5(a) is a side view schematic diagram of a partially completedthin-film transistor device according to the present invention;

FIG. 5(b) is a side view schematic diagram of a partially completedthin-film transistor device according to the present invention;

FIG. 6 is a side view schematic diagram of a partially completedthin-film transistor device according to the present invention;

FIG. 7 is a side view schematic diagram of a partially completedthin-film transistor device according to the present invention;

FIG. 8 is a side view schematic diagram of a partially completedthin-film transistor device according to the present invention;

FIG. 9 is a side view schematic diagram of a thin-film transistor deviceaccording to the present invention;

FIG. 10 is a side view schematic diagram of a thin-film transistordevice according to the present invention; and

FIG. 11 is a flow diagram illustrating a preferred method of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

As mentioned above, there is a need for an improved structure and methodfor producing a planar polymer transistor which does not have theproblems-inherent with the prior art devices, such as the cornerthinning problem due to topography, and having the most sensitiveportion of the body element exposed to process-induced contamination.According to the present invention, a new and improved structure of athin-film transistor is disclosed, as well as a method for producing thesame.

Referring now to the drawings, and more particularly to FIGS. 4 through11, there are shown preferred embodiments of the method and structuresaccording to the present invention. Specifically, FIG. 4 shows apartially completed thin-film transistor device 50 comprising aninsulating polymer 120 coated on top of a thin layer of wax 110 formedon a substrate carrier 100. The thin layer of wax 110 allows for theease of material transference at a later stage. The substrate 100 can beglass, ceramic, or a semiconductor wafer. Polymer 120 can be a flexiblesubstrate such as a polyester or a polyimide, or it can be a stiffermaterial such as polycarbonate.

Layer 110 can also be a photoresist or photosensitive polyimide whereinthe solubility in solvents significantly increase upon exposure to lightfor the ease of detachment. Alternatively, the layer 110 can be a thinlayer of polyimide which can be photoablated with a low power excimerlaser.

A layer of conductive polymer 125, such as polyaniline, poly(pyrrole),poly(ethylene dioxide thiophene), or a conductive paste such as metal orgraphite colloidal inks, or a conductive metal such as Au, Pd, Al, Cu,is then deposited on top of the insulating polymer 120, as shown in FIG.5(a). The conductive polymer 125 can be patterned by using aconventional lithographic patterning method or a printing method whichresults in pads 130, 140 and 150, which is shown in FIG. 5(b). Pads130,140 and 150 can be used as the source, gate, and drain conductors,respectively. The spaces between the pads are well-controlled so as toavoid forming any topography, and the method to do this is well-known inthe art.

The conductive material 125 can also be formed by any number of printingmethods, such as inkjet printing, which has been described inSirringhaus et al., “High-Resolution Inkjet Printing of All-PolymerTransistor Circuits,” Science, Vol. 290, pp. 2123-2126 (2000); screenprinting as described in Bao et al., “High-Performance PlasticTransistors Fabricated by Printing Techniques,” Chem. Mater., Vol. 9,pp. 1299-1301(1997); and the soft-lithographic technique micromolding incapillaries as described in Bao et al., “Printable Organic and PolymericSemiconducting Materials and Devices,” J. Mater. Chem., Vol. 9, pp.1895-1904 (1999); the complete disclosures of which are hereinincorporated by reference.

As shown in FIG. 6, a second layer of insulating polymer 160 is coatedon top of pads 130, 140, and 150, and within the spaces therein. Thispolymer 160 is preferably a high dielectric constant polymer. Someexamples of high dielectric constant polymer composites are indicated in“High Dielectric Constant Ceramic Powder Polymer Composites,” B. Y.Cheng et al., Appl. Phys. Lett. (USA), Vol. 76, No. 25, 19, Jun. 2000,P3804-6, and U.S. Pat. No. 5,739,193, the complete disclosures of whichare herein incorporated by reference. For example, a ferroelectricpolymer can be used as the gate dielectric for the organic transistor toimprove the transconductance. Suitable insulating polymers include PMMA,polyimide or polyvinylphenol. A chemical-mechanical polish process canbe carried out, if necessary, since the polymer is supported by a firmcarrier. A pair of contacts 170 and 180 are formed using the similarmethod mentioned in FIGS. 5(a) and 5(b) for source and drain contacts,respectively.

In FIG. 7, a layer of semiconductive polymer or oligomer with a uniformthickness 190 is coated on top of the second insulating polymer layer160 and contacts 170 and 180, and is immediately protected by a thirdlayer of insulating polymer 200.

The semiconductive organic material is sensitive to contamination;therefore, the properties of the material will be degraded if notimmediately covered with a layer of protective coating. Therefore, afterthe material 190 is coated, a thin polymer 200 is immediately deposited.The semiconductive organic material is prevented from being exposed byany chemical. A proper thermal treatment is carried out after thesemiconductive organic material is covered by a thick insulatingpolymer. In most instances, the performance of the organic semiconductoris very sensitive to temperature. Organic semiconductors are notgenerally exposed to thermal treatment.

Next, as detailed in FIG. 8, the composite 50 is flipped upside-down andthen bonded to a second carrier layer 220 with a second precoated layerof wax 210 disposed therebetween. Simultaneously, the first carrier 100and the first thin layer of wax 110 are removed.

Then, the composite 50 is etched, and patterned sections 230 emerge todefine the whole transistor 50, which is illustrated in FIG. 9. Theetching process etches through the protective layer 120, the contactpolymer pads 130, 140, and 150, the high-k dielectric polymer 160, thesemiconductive organic material 190, and stops at the polymer substrate200. The etching can be accomplished in an oxygen plasma.

Then, as shown in FIG. 10, another insulating polymer 270 is coated onthe composite 50 right after etching and fills the patterned sections230. This can be done in-situ in the same reactor such that thesemiconductive polymer 190 will not become contaminated (or poisoned).Contacts to the source 240, gate 250, and drain 260 are formed with aconductive material, polymer, or metal, followed by achemical-mechanical polish.

Generally, FIG. 10 illustrates a completed fully planarized thin-filmtransistor device 50 comprising a carrier layer 220, a first insulatinglayer 200 over the carrier layer 220, a fully planarizedcontaminant-free semiconductor layer 190 over the first insulating layer200, a second insulating layer 160 over the semiconductor layer 190, athird insulating layer 270 adjacent to sides of the semiconductor layer190, and a plurality of conductive contacts 150/180, 130/170 connectedto the semiconductor layer 190, wherein the first 200, second 160, andthird 270 insulating layers each comprise one of a polyester and apolyimide material. In another embodiment, the first 200, second 160,and third 270 insulating layers each comprise a polycarbonate material.The thin-film transistor device 50 further comprises an adhesive layer210 connected to the carrier layer 220, wherein the adhesive layer 210comprises one of a photoresist and a photosensitive polyimide material.Additionally, the thin-film transistor device 50 further comprisessource 240, drain 260, and gate 250 regions connected to the conductivecontacts 150/180, 130/170, 140, respectively. Furthermore, thesemiconductor layer 190 is adjacent to each of the first 200, second160, and third 270 insulating layers, wherein the first 200, second 160,and third 270 insulating layers surround the semiconductor layer 190.

The entire process of forming a fully planarized polymer thin-filmtransistor 50 is further shown in the flow diagram of FIG. 11. Theprocess comprises using a first planar carrier 100 to process 300 afirst portion of the device 50 including gate 140, source 150, and drain130 body elements. Preferably, the thin-film transistor 50 is made withall organic material. The gate dielectric 160 can be a high-k polymer toboost the device performance. Then, the partially-finished devicestructures are flipped 310 upside-down and transferred 320 to a secondplanar carrier 200. Next, a layer 210 of wax or photo-sensitive organicmaterial is deposited 330 as the temporary glue. The device 50,including its body area, is then defined 340 by an etching process.Contacts 240, 250, 260 to the devices are formed 350 by conductivematerial deposition and chemical-mechanical polish.

The novel features of the present invention are several. Broadly, thepresent invention provides for a high-performance transistor due tounique structural and process flow. Specifically, all functionalcomponents are preferably made of polymeric materials (semiconductive,conductive, low-k insulative, and high-k insulative materials).Furthermore, the carrier is preferably a wafer, glass carrier, orpolymer, and can be rigid or flexible. However, the size is not limitedby the wafer size and is adaptable to large format carriers. Also, theentire structure, including the semiconductor body, gate, source/drain,the interface between the body and the gate, and the drain/source areall fully planarized so that there is no electrical performancedegradation due to the corner thinning between the semiconductor bodyand the source/drain region. Moreover, the structure is fabricated in asimple and cost-effective manner, which allows for the fabrication ofboth N-FET and P-FET transistors. Finally, the semiconductor body isplanarized, and its interface with the source/drain and gate dielectricis fully protected from subsequent processing.

Furthermore, unlike conventional polymer thin-film transistors, theinvention produces fully planarized devices so that there is no cornerthinning problem. Another advantage of the new polymer device is thatthe most sensitive area of the device, the body, which is made of anorganic semiconductor, is fully protected, before any processing steps,to avoid the possibility of being contaminated by the environment.Moreover, the organic semiconductor is fully enveloped by a plurality ofinsulator layers 200, 160, 270 so as to avoid contamination.

While the invention has been described in terms of preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims.

1. A thin-film transistor device comprising: a carrier layer; a firstinsulating layer over said carrier layer; a fully planarizedsemiconductor layer over said first insulating layer; a secondinsulating layer over said semiconductor layer; a third insulating layeradjacent to sides of said semiconductor layer; a plurality of conductivecontacts connected to said semiconductor layer; source and drain regionsconnected to said conductive contacts; and a gate region connected tosaid conductive contacts, wherein said source, drain, and gate regionsare co-planar.
 2. The device of claim 1, wherein the first, second, andthird insulating layers each comprise one of a polyester and a polyimidematerial.
 3. The device of claim 1, wherein the first, second, and thirdinsulating layers each comprise a polycarbonate material.
 4. The deviceof claim 1, further comprising an adhesive layer connected to saidcarrier layer, wherein said adhesive layer comprises one of aphotoresist and a photosensitive polyimide material.
 5. The device ofclaim 4, wherein said thin-film transistor is fully planarized.
 6. Thedevice of claim 1, wherein said semiconductor layer is contaminant-free.7. The device of claim 1, wherein said semiconductor layer is adjacentto each of the first, second, and third insulating layers, and whereinsaid first, second, and third insulating layers surround saidsemiconductor layer.
 8. A fully planarized thin-film transistor devicecomprising: a carrier layer; a first insulating layer over said carrierlayer; a contaminant-free semiconductor layer over said first insulatinglayer; a second insulator layer over said semiconductor layer; a thirdinsulating layer adjacent to sides of said semiconductor layer; aplurality of conductive contacts connected to said semiconductor layer;source and drain regions connected to said conductive contacts; and agate region connected to said conductive contacts; wherein said source,drain, and gate regions are co-planar, and wherein the first, second,and third insulating layers surround said semiconductor layer.
 9. Thedevice of claim 8, wherein the first, second, and third insulatinglayers each comprise one of a polyester and a polyimide material. 10.The device of claim 8, wherein the first, second, and third insulatinglayers each comprise a polycarbonate material.
 11. The device of claim8, further comprising an adhesive layer connected to said carrier layer,wherein said adhesive layer comprises one of a photoresist and aphotosensitive polyimide material.
 12. The device of claim 8, whereinsaid semiconductor layer is adjacent to each of said first, second, andthird insulating layers.
 13. A thin-film transistor device comprising: asubstrate; a first insulating layer over said substrate; a fullyplanarized contaminant-free semiconductor layer over said firstinsulating layer; a second insulating layer over said semiconductorlayer; a third insulating layer adjacent to sides of said semiconductorlayer; a plurality of conductive contacts connected to saidsemiconductor layer; source and drain regions connected to saidconductive contacts; and a gate region connected to said conductivecontacts, wherein said source, drain, and gate regions are co-planar,and wherein said semiconductor layer is adjacent to each of the first,second, and third insulating layers.
 14. The device of claim 13, whereinthe first, second, and third insulating layers each comprise one of apolyester and a polyimide material.
 15. The device of claim 13, whereinthe first, second, and third insulating layers each comprise apolycarbonate material.
 16. The device of claim 13, further comprisingan adhesive layer connected to said carrier layer, wherein said adhesivelayer comprises one of a photoresist and a photosensitive polyimidematerial.
 17. The device of claim 13, wherein said thin-film transistoris fully planarized.
 18. The device of claim 13, wherein the first,second, and third insulating layers surround said semiconductor layer.